A Cyclometalated NHC Iridium Complex Bearing a Cationic (η5 -Cyclopentadienyl)(η6 -phenyl)iron Backbone*.

ABSTRACT

Nucleophilic substitution of [(η5 -cyclopentadienyl)(η6 -chlorobenzene)iron(II)] hexafluorophosphate with sodium imidazolate resulted in the formation of [(η5 -cyclopentadienyl)(η6 -phenyl)iron(II)]imidazole hexafluorophosphate. The corresponding dicationic imidazolium salt, which was obtained by treating this imidazole precursor with methyl iodide, underwent cyclometallation with bis[dichlorido(η5 -1,2,3,4,5-pentamethylcyclopentadienyl]iridium(III) in the presence of triethyl amine. The resulting bimetallic iridium(III) complex is the first example of an NHC complex bearing a cationic and cyclometallated [(η5 -cyclopentadienyl)(η6 -phenyl)iron(II)]+ substituent. As its iron(II) precursors, the bimetallic iridium(III) complex was fully characterized by means of spectroscopy, elemental analysis and single crystal X-ray diffraction. In addition, it was investigated in a catalytic study, wherein it showed high activity in transfer hydrogenation compared to its neutral analogue having a simple phenyl instead of a cationic [(η5 -cyclopentadienyl)(η6 -phenyl)iron(II)]+ unit at the NHC ligand.